CA2249242C

CA2249242C - Surface effect vessel hull

Info

Publication number: CA2249242C
Application number: CA002249242A
Authority: CA
Inventors: Howard D. Harley
Original assignee: Howard D. Harley
Priority date: 1996-03-21
Filing date: 1997-03-06
Publication date: 2001-05-15
Anticipated expiration: 2017-03-06
Also published as: JP4050319B2; EP0898543A1; CN1216508A; DK0898543T3; KR20000064732A; CN1071665C; DK898543T3; EE03558B1; WO1997034796A1; NO984400D0; IL126302D0; JP2000506814A; PL328945A1; EP0898543B1; PT898543E; ES2193354T3; BR9709294A; HK1019218A1; NO984400L; AU705766B2

Abstract

A surface effect hull (10) particularly suitable for use with a catamaran vessel. The twin hulls (12) each comprise a V-shaped portion (formed by faces 38 and 40) and a recess portion (36) that receives pressurized gas therein. The V-shaped bow portion creates dynamic lift and the pressurized air portion creates an air cushion for reduction of drag.

Description

ENT1TLEL): Surface Effect Vessel Hull BACKGROUND OF THE INVENTION

1. FELD OF THE INV~NTION
The present invention relates to marine vessel hulls utilizing pressurized gas cushions maintained in a recess in a portion of the bottom of the hull ror reduction of water drag on the hull, thereby increasing the speed and fuel efficiency of the vessel.
This invention more particularly relates to a marine vessel havin,~ a catamaran configuration with each catamaran side hull havin~ a pressurized gas cushion.

2. DESCRIPTION OF THE PRIOR ART
One of the primary objectives in boat design is to reduce the amount of drag caused by the interface of the hull with the water surface. Early planing hulls were designed so that forward motion of the hull raised the vessel to cause it to ride on a smaller portion of its hull surface resulting in reduced hull-to-water friction. The design of hydrofoil vessels further reduced hull contact with the water by ~tt~hjng foils to the hulls upon which the boats ride at high speed. Some marine vessels interpose a film of air between the vessel's hull and the water to reduce the hull-to-water friction. One example is illustrated in United States Patent 3.191.572 issued to H. A. Wilson in which a tri-hulled vessel has air introduced alon~ the bottom of each hull. This air is allowed to stream freely from the stern of the vessel. U.S. Patent 4,031,841 issued to Bredt also discloses the technology for an air film hull. The Bredt and Wilson hulls still ride with the hull relatively low in the water so that much of the sides of the hulls m~inl~in contact with the water. but the dra~ between a portion of the bottom is somewhat reduced by a film of air mixed with water.
Surface effect ships were an improvement over the air film hulls as the hulls ofsurface effect ships are raised out of the water by a pressurized air cushion that is partially captured within the hull of the vessel. The prior art of air cushion vessel hull designs have contained the air cushion with flexible seals, which are a rubberized curtain, either all around the vessel as in the case of the hovercraft air cushioned vessels, or WO 97/34796 PCTrUS97/03390 across the front and the hack of the vessel with thin parallel side hulls that provide a side seal for the air cushion as in the case of surface effect ships. The flexible seals reduce the amount of air lost from the air cushion but create a rough ride. "a cobble stone ride,"
even in smooth water. As the surface of the water becomes rougher the flexible seals can 5 be separated from each other. causin~ further deterioration in ride quality. Also. in rough water the flexible seals frequently fail to m~int;lin the air cushion, causing the craft's hull to drop lower into the water until the seal is regained and the air cushion is reestablished. The loss of the air cushion increases the hull contact with the water increasing the hull-to-water friction and significantly slowing the vessel. Seals are a high o maintenance problem with frequent breakage that results in permanent loss of air cushion and a slow ride to the repair yard. Such surface effect ships are disclosed by U.S.
Patents 5.415,120. and 4.392.445 issued to Donald E. Bur~ and U.S. Patent 4,523,536 issued to Mark H. Smoot.
Notwithstandin~ the existence of such prior art for surface effect ships. it remains ~s clear that there is a need for a vessel which will maintain a relatively smooth ride and maintain the air cushion whether the water is smooth or rough without the use of flexible seals. Also, there is a need to improve the stability of surface effect ships which are notoriously unstable in rough water.

CA 02249242 .998-09-.7 W O 97/34796 PCT~US97/03390 SU~M ARY OF THE I~rVENTION
The present invention relates to a surface effect ship havin~ a pair of V-shapedhulls having air cushion recesses that receive pressurized air to provide an efficient.
stable, smooth~ hi~h speed ride. The surface effect vessel hull comprises two catamaran 5 hulls joined by a deck surface. each catamaran hull defining a longitudinal dimension.
Each catamaran hull comprises a bottom. having an exterior surface; and opposing sides.
having first and second ends, attached to the bottom and extending upwardly therefrom, the sides curving inwardly and joining together at the first end to form a bow and bein~
connected together at the second end by a transversely extending transom. A step, a o generally planar surface. extends inwardly from the bottom generally perpendicular to the lon~itudin~l dimension so that a plane defined by the step separates each catamaran hull into two parts, a ~ow portion extending forward of the plane and an air cushion portion extending rearwardly of the plane.
The bow portion of the bottom comprises a first face and a second face that are 15 joined together to form a v-shape that extends from proximal the bow to the step. The apex of the v-shape defines the keel of the bow portion. The first and second face each define an angle with a horizontal plane which is defined as the dead rise angle of the hull.
A cross section of the hull generally perpendicular to the longitudinal dimension defines a dead rise angle that lies within a range of 45~-65~. The dead rise angle decreases to 20 less than 25~ as defined by the intersection between the step and the bottom of the bow portion.
The air cushion portion of the bottom has a recess formed therein. the recess extending inwardlv from the exterior surface of the bottom incorporating the step as one side of the recess and the recess extending rearward from the step to the transom. The 25 recess defines secondar,v catamaran hull sections that extend from the step to a point adjacent the transom. A pressurized air generation means. that is well known in the art, is connected in fluid flow communication with the air cushion recess.
- The invention accordingly comprises an article of manufacture possessing the features, properties, and the relation of elements which will be exemplified in the article 30 hereinafter described. and the scope of the invention will be indicated in the claims.

WO 97/347g6 PCT/US97/03390 BRIEF DESCRIPTION OF THE DRAWINGS
For a fuller understanding of the nature and objects of the invention, referenceshould be had to the followin~ detailed description taken in connection with theaccompanying drawings, in which:
S FIGURE 1 is a perspective view of the surface effect vessel hull of this invention.
FIGURE 2 is a bottom plan view of the invention of FIG. 1.
FIGURE 3 is right side elevation of the surface effects hull.
FIGURE 4 is a sectional elevation view taken along line 4-4 of FIG 2.
FIGURE 5 is a sectional elevation view taken along line 5-5 of FIG 2.
~0 FIGURE 6 is a sectional elevation view taken along line 6-6 of FIG 2.
FIGURE 7 is a sectional elevation view taken along line 7-7 of FIG 2.
FIGURE 8 is a sectional elevation view taken along line 8-8 of FIG 2.
FIGURE 9 is a sectional elevation view taken along line 9-9 of FIG 2.
FIGURE 10 is a sectional elevation view taken along line 10-10 of FIG 2.
Similar reference characters refer to similar parts throughout the several views of the drawings.

DETAIL~D DESCRIPTION
A preferred embodiment for the surface effect vessel hull is illustrated in the drawin~ Fi~ures 1-1() in which the surface effect vessel is generally indicated as 10.
Referring first to Fig. 1 it can be seen that the vessel hull 1~) comprises a pair of s catamaran hulls 12 that are )oined to one another by a deck 14.
As shown in Fig. 2, each catamaran hull has a longitudinal dimension A. and comprises a bottom 16. that has an exterior surface 18, a pair of opposing sides 20 that are attached to the bottom 16 and extend upwardly therefrom. For the purposes of this specification, the chine 22 defines the line of attachment of the sides 20 to the bottom 16.
o The first ends 24 of each side 20 are joined to form the bow 26, and the second ends 28 are connected to one another by a transom 30 that extends transversely therebetween.
A step 32. which can be seen most clearly in Figs. 3 and 8, extends inwardly from the bottom 12, generally perpendicular to the longitudinal dimension A. As seen in Fig. 2, the step 32 lies in a plane B that defines a bow portion 34 exten~ing forwardly, including the bow 26, and an air cushion portion 36 extending rearwardly of said plane andincluding the transom 30. In a preferred embodiment, the bow portion 34 comprises S0 percent of the overall length of the vessel from bow 24 to the transom 30, that is the step 32 is ~enerally at the mid point between the bow 26 and the transom 32. In otherembodiments, the step 32 may be located between 42 percent and B0 percent of thelongitudinal length of the vessel 10 as measured from the bow 26 and still provide a vessel with acceptable characteristics. The bow portion 34 of the bottom 16 comprises a first face 38 and a second face ~0 that are joined along the keel 42 to forrn a V-shape.
Each face~ 38 and 40, forms an angle C with a horizontal plane, angle C is defined as the dead rise of the hull. At a cross section of the bottom 16 proximal the bow 26, as shown in Fig. 5, the an~le C is preferably SS degrees, however in other embodiments the angle C proximal the bow 26 may lie within the range of 30 degrees to 65 degrees and still function satisfactorily. In a preferred embodiment, the angle C gradually decreases ~ to 16-20 degrees at the transom 30, angle C' as shown in Fi8 8. In other embodiments, the angle C' may lie within the range of 25 degrees to 0 degrees and still function satisfactorily.
The air cushion portion 36 of the bottom 16 has an air cushion recess 44 formed therein that extends inwardly from the exterior surface 18 of the bottom 16. and extends W O 97/34796 PCT~US97/03390 rearwardly to proximal the transom 30. The recess 44 is bounded by the step 32 at the forward end, slopiny recess sides 46 that extend rearward to the transom 30 and a downwardly curving top 48, which in the embodiment disclosed! tapers to nothing as shown in Figs. 9 and 10. In other embodiments the air cushion recess 44 may comprise many different shapes that are well known in the art. the shape shown is but one example of a shape that works effectively. The recess sides 46 and the sides 20 of the catamaran hull 12 form a pair of secondary catamaran hull sections 50 that extend from the step 32 to the transom 30. Each secondary catamaran hull section S0 has a fin 52 formed thereon that extends ,~enerally the length of the secondary catamaran hull section 46. In a preferred embodiment. the length of the recess 44 (the lon~itutlin~l length of the recess sides 46) is greater than the transverse width (the athwartship dimension) of the recess 44 as measured between the fins 52 at right angles to the longitu~lin~l dimension A.
In a preferred embodiment. the fins 52 extend from proximal the transom to a point forward of the step 32. onto the bottom surface 18 of the bow portion 34, the point forward of the step bein~ at a distance from the step that lies within the ran~e of 2.9 percent to 7.1 percent of the overall longi~u-lin~l dimension of the vessel lO. In a preferred embodiment the fins 52 extend 5 percent of the overall longitu~lin~l dimension of the vessel 10, for example. on a 100 foot vessel the fins 52 will extend five (5) feet beyond the step 32. Extension of the fins 52 beyond five (5) percent causes the ride of the vessel to degrade without gaining any increased protection of the air cushion recess 44~ The vertical dimension of the fin 52, measured generally normal to the hull.preferably extends one half to l percent. of the overall longitudinal dimension of the vessel hull lO, from the bottom surface l8, e.g. approximately 9 to 12 inches for a vessel 10 having a lO0 foot longitudinal dimension.
The portion of each fin 52 that is distal the boat 10 comprises a f1n keel portion 54. The fin keel portions 54 of each fin 52 lie generally in the same plane with one another and generally in the same plane as a portion of the keel 42 of the bow portion 34 of the hull 10 that is proximal to the step 32.
A pressurized air ~eneration means, shown generally as 58 is preferably mounted within the vessel 10 and is connected by duct 60 to outlets 62 formed in the top 48 of the recess 44~ Devices 58 for supplying air under pressure are well known in the art and may be provided as individual units as shown in Fig. 3, or a single unit may be used that .. . . . .

W O 97/34796 PCTrUS97/03390 is connected to each outlet 62 by extended ducts 60. The devices may be operated from their own motors or may be operated by a power take-offs from inboard motors.
The surface effect hull 10 may be constructed of fiber glass. synthetic resins.
composites. aluminum. steel~ or any other material that is suitable for the purpose. Boats or ships constructed using the surface effect hull design disclosed may use any drive method including standard outboard motors for smaller boats and larger inboard gas or diesel enyines or turbine engines for large vessels. The amount of power required to operate such a vessel will be far less than that required by a conventional boat or ship.
Having thus set forth a preferred construction for the surface effe~ct hull 10 of this o invention, it is to be remembered that this is but a preferred embodiment. Attention is not invited to a description of the use of surface effect hull 10. Certainly many different super structures may be constructed on the hull 10 depending on the use for which the vessel is intended. including but not limited to racing craft, pleasure yachts, and for freight and/or passenger transport.
The surface effect hull 10 discussed below is discussed in relation to a hull 10 that has a longitu~lin~l dimension of 100 feet. Various size hulls 10 may be constructed with generally proportional dimensions, however, these dimensions may be adjusted by those skilled in the art depending upon the specific use that is intPn-led for the vessel utili7ing the surface effect hull 10. The surface effect hull 10 does not incorporate any flexible 20 seals, elimin~ting the problems associated therewith, a rough ride, high m~int~n~n~e, control problems. high hump drag (meaning ships with flexible seals are hard to get up on the cushion, to get over the hump. which takes a lot of power that is not necessary when the vessel is on the cushion). The surface effects hull 10 is a catamaran with twin hulls that each have a pressurized air cushion over approximately 50 percent of its length.
25 Each hull 12 has a bow portion 34 that comprises the rem~ining 50 percent of the longitudinal dimension. The bow portion 34 of each catarnaran hull 12 has a V-bottom 16 with a sharp entry proximal the bow 26. a dead rise of approximately 55 degrees, the dead rise is reduced to less than 25 degrees proximal the step 32, easily creating dynamic lift as the vessel's speed increases so that the vessel easily begins to plane, as boats 30 without air cushions have operated for years. The sharp entry bow portion 34 is designed to deflect the approaching waves both downward and sideways in a progressive manner over a substantial part of the craft's length. The water passing beneath the air cushions W O 97/34796 PCT~US97/03390 is conse~uently modified to be essentially horizontal. even when the surface effect ship 1() is operating in significant seas. The advantages of this design. which modifies the ~low of the approaching waves before they reach the air cushion portions 36 of the hull 12 are considerable. Flexi'nle seals used by conventional surface effect ships are s unnecessary. elimin~tin~ the high maintenance costs and down time required for repair of flexible seals. Without the modification of the waves to e~ ntiAlly a horizontal configuration. the waves strike the flexible seals of conventional surface effect ships causing reduction in cushion volume and variations in the cushion pressure creating additional lift power requirements, and along with bow .~l~mming are the primary factors o that can result in a rough ride. The sharp entry of the bow portion 34 of the two catamaran hulls 12 greatly reduces pitching, green water and spray compared with the conventional surface effect ship.
However. once on plane there remains a large portion of the vessel bottom 12 that would remain wetted, in contact with the water, creating drag. By pl~rrm~îlt of a pressurized air cushion under this portion of the hull, the drag is greatly reduced as the air cushion portion 36 of the surface effect hull 10 rides on air. Therefor the surface effect hull 10 combines dynamic lift with lift from a pressurized air cushion, making it easy for the vessel to reach plane and yet significantly reduces the drag on the hulls 12.
The bow portion 34 of the hull 12 has only a small wetted area to create drag due to the hi~hly efficient dynamic lift created by the bow portion 34. The pressurized air cushions, which create air platform lift, cover the majority of the hull surface of the air cushion portion 36 of the hull 12 that is in direct contact with the water reducing drag. This combination gains from the best of dynamic lift and air platform lift to create a highly efficient hull design not previously obtained in successful boat and ship hull design.
2s Use of twin hulls 12, each with a separate pressurized air cushion increases the stability without appl~ciably increasing the drag. The separated hulls and separated air cushions create a large roll-restoring force which produces a surface effect ship that is not very center-of-gravity sensitive. Stiffness and damping in roll are greatly increased because each air cushion acts on the cushion separation arm to provide roll stability. The brid~e span between the twin hulls 12 is much smaller than the bridge span on a conventional surface effect ship of the same beam. Such wide spacing on the conventional surface effect ship creates a heavy ship as wide spacing between the hulls W O 97/34796 PCT~US97/03390 requires very si~nificant structural reinforcement. Twin hulls 12 also increase the efficiency of performance at all speeds compared with the desi~n of a single cushion surface effect ship that can only be designed for efficiency at one speed. Performance improvements also result from air cushions recesses that have a lon~itudinally extending dimension that is appreciably greater than the athwartship dimension.
Placement of the air cushion recess 44 too far forward reduces the dynamic lift and exposes the air cushion recess 44. which would then require the use of a flexible curtain as in the prior art conventional surface effect ships. Beginning the air cushion recess 44 too far from the bow 26 would increase the drag appreciahly. A SO percent o bow portion 34 combined with a 50 percent air cushion portion 36 has been found to be a preferred embodiment for the surface effect hull 10.
The air cushion recess 44 must be protected so that water does not enter the recess 44 or an unacceptable amount of air escape forward. The sharp entry that gradually reduces to a dead rise of less than 25~ deflects the approaching waves both downward s and sideways and modifies the water as it approaches the air cushion recess 44 to es.~nti~lly horizontal flow. The fins 52 that extend forward of the air cushion recess 44 shield the air cushion recess 44 preventing the escape of air and the entry of water into the recess 44 so that the air cushion is m~int:~inPd.
It will thus be seen that the objects set forth above, among thnse made apparentfrom the preceding description. are efficiently attained and, since certain changes may he made in the above article without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
It is also to be understood that the following claims are intended to cover all of 2~ the generic and specific features of the invention herein described. and all a statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.
Now that the invention has been described,

Claims

1. A surface effect vessel hull comprising:
two catamaran hulls joined by a deck, each catamaran hull defining a longitudinal dimension;
each said catamaran hull comprising a bottom having an exterior surface, opposing sides attached to said bottom and extending upwardly therefrom, the sides joining together to form a bow, and a transom connecting said sides and being attached to and extending upwardly from said bottom, a step extending inwardly from said bottom generally perpendicular to said longitudinal dimension, said step lying in a plane passing through said hull generally transverse to said longitudinal dimension defining a bow portion extending forward of said plane and an air cushion portion extending rearwardly of said plane;
said bow portion of each said catamaran hull bottom comprising a first face and a second face joined to form a V-shape that extends from proximal said bow to said step, a line formed by said intersecting faces defining a keel of said bow portion, said first and second faces each defining an angle with a horizontal plane passing through said keel, said angle at a cross-section proximal said bow is at least 45 degrees, said angle diminishing to less than 25 degrees at said step;
said air cushion portion of each said catamaran hull bottom having a recess formed therein, said recess extending inwardly from said exterior surface of said bottom, said recess extending rearward from said step to proximal said transom, said recess defining secondary catamaran hull sections extending from said step to said transom;
pressurized air generation means connected in fluid flow relation to said air cushion recess.

2. A surface effect vessel hull as in claim 1 wherein said bow portion of each catamaran hull has a longitudinal dimension from said bow to said step that lies within the range of 35 to 80 percent of the longitudinal length of said catamaran hull from said bow to said transom.

3. A surface effect vessel hull as in claim 1, wherein said angle diminishes from at least 55 degrees proximal said bow to 20 degrees or less at said step.

4. A surface effect vessel hull as in claim 1 comprising a fin extending downwardly from each secondary catamaran hull section, said fin extending from proximal said transom to a point forward of said step, said point forward of said step being at a distance from said step that lies within the range of 2.9 percent to 7.1 percent of the overall longitudinal dimension of said vessel.

5. A surface effect vessel hull as in claim 4, wherein each said fin comprises a keel portion, said fin keel portion of each said catamaran hull section lies generally in the same plane with one another and generally in the same plane as the keel of said bow portion of said hull proximal said step.

6. A surface effect vessel hull as in claim 1 comprising catamaran hulls having longitudinal axes generally parallel to one another and said catamaran hulls being spaced apart from one another.